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Stiffness of the healing human Achilles tendon
Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Achilles tendon ruptures in humans are followed by a long period of immobilisation, rehabilitation and limitations of physical activity and sometimes work also. This prolonged period probably leaves a marginal for improvement in the management of this injury. Animal studies have shown that there are several possibilities to influence and improve tendon healing.

The aim of this thesis was to find a way to examine the mechanical properties of the healing human Achilles tendon and, by using that method, to gain a better understanding of the tissue properties and healing process in these tendons. It was also our aim to use our knowledge from animal studies in an attempt to improve tendon healing in humans.

We developed a radiological method using radiostereophotogrammetric analysis (RSA) and computed tomography (CT), which enabled us to measure the stiffness of the healing Achilles tendon. The results of these measurements, as early as 7 weeks after injury correlated with the late clinical results in all studies. Clinical results were measured using a heel-raise test comparing the injured with the non-injured tendon. We could not find a significant difference in stiffness between patients treated surgically or non-surgically. Neither could we demonstrate that platelet-rich plasma improved the mechanical properties of the healing tendon or the clinical outcome, within the limits of the statistical power. In contrast, patients following a specific training programme with early tension loading of the tendon twice a day developed stiffer tendon tissue later in the healing process.

Since RSA is unsuitable for routine clinical use, we evaluated the possibility to use radiodensity findings from CT as a proxy for healing and its correlation to mechanical and clinical results. Density and mechanical properties correlated strongly when analysing all time points together, but only weakly at each particular point in time. Density may still be useful in describing mechanical properties at a later stage of repair, but this remains to be seen.

In conclusion, these studies show that early mechanical properties correlate to late clinical outcome and that the early use of daily tension loading sessions leads to an improvement in the mechanical properties of the tendon tissue.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. , 59 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1356
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-91727ISBN: 978-91-7519-674-9 (print)OAI: oai:DiVA.org:liu-91727DiVA: diva2:618919
Public defence
2013-06-04, Elsa Brändströmsalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2013-04-30 Created: 2013-04-30 Last updated: 2013-05-13Bibliographically approved
List of papers
1. Mechanical properties during healing of Achilles tendon ruptures to predict final outcome: A pilot Roentgen stereophotogrammetric analysis in 10 patients
Open this publication in new window or tab >>Mechanical properties during healing of Achilles tendon ruptures to predict final outcome: A pilot Roentgen stereophotogrammetric analysis in 10 patients
2007 (English)In: BMC Musculoskeletal Disorders, ISSN 1471-2474, E-ISSN 1471-2474, Vol. 8Article in journal (Refereed) Published
Abstract [en]

Background. There are presently few methods described for in vivo monitoring of the mechanics of healing human tendon ruptures, and no methods for prediction of clinical outcome. We tested if Roentgen stereophotogrammetric analysis (RSA) can be used to follow the restoration of mechanical properties during healing of ruptured Achilles tendons, and if early measurements can predict clinical results. Methods. Achilles tendon repair was studied with RSA in 10 patients with a total rupture. Tantalum beads were implanted in conjunction with surgical repair. The patients were evaluated at 6, 12 and 18 weeks, and after 1 year. RSA was performed with two different mechanical loadings, and the strain induced by increasing load was measured. The transverse area was determined by ultrasound. CT scan at 12 weeks confirmed that the tantalum beads were located within the tendons. Functional testing was done after 1 year. A heel raise index was chosen as primary clinical outcome variable. Results. The strain was median 0.90, 0.32 and 0.14 percent per 100 N tendon force at 6 weeks, 18 weeks and one year respectively. The error of measurement was 0.04 percent units at 18 weeks. There was a large variation between patients, which appears to reflect biological variation. From 6 to 18 weeks, there was a negative correlation between increase in transverse area and increase in material properties, suggesting that healing is regulated at the organ level, to maximize stiffness. Modulus of elasticity during this time correlated with a heel raise index at one year (Rho = 0.76, p = 0.02). Conclusion. We conclude that the RSA method might have potential for comparing different treatments of Achilles tendon ruptures. © 2007 Schepull et al, licensee BioMed Central Ltd.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-47632 (URN)10.1186/1471-2474-8-116 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
2. Early E-modulus of healing Achilles tendons correlates with late function: Similar results with or without surgery
Open this publication in new window or tab >>Early E-modulus of healing Achilles tendons correlates with late function: Similar results with or without surgery
2012 (English)In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 22, no 1, 18-23 p.Article in journal (Refereed) Published
Abstract [en]

Non-operative treatment of Achilles tendon ruptures is associated with an increased risk of rerupture. We hypothesized that this is due to inferior mechanical properties during an early phase of healing, and performed a randomized trial, using a new method to measure the mechanical properties. Tantalum markers were inserted in the tendon stumps, and tendon strain at different loadings was measured by stereo-radiography (Roentgen stereophotogrammetric analysis) at 3, 7 and 19 weeks and 18 months after injury. Thirty patients were randomized to operative or non-operative treatment. The primary out-come variable was an estimate for the modulus of elasticity at 7 weeks. Strain per force, cross-sectional area and tendon elongation were also measured. The functional outcome variable was the heel-raise index after 18 months. There was no difference in the mean modulus of elasticity or other mechanical or functional variables between operative and non-operative treatments at any time-point, but strain per force at 7 and 19 weeks had a significantly larger variation in the non-operative group. This group, therefore, might contain more outliers with poor healing. The modulus of elasticity at 7 weeks correlated with the heel-raise index after 18 months in both treatment groups (r2=0.75; P=0.0001). This correlation is an intriguing finding.

Place, publisher, year, edition, pages
John Wiley and Sons, 2012
Keyword
achilles tendon rupture, tendon healing, biomechanics, modulus of elasticity
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-75106 (URN)10.1111/j.1600-0838.2010.01154.x (DOI)000298984300004 ()
Note
Funding Agencies|Swedish Medical Research council||Swedish Center for Sports Medicine Research||King Gustav V and Queen Victoria Free Mason fund||Available from: 2012-02-21 Created: 2012-02-17 Last updated: 2017-12-07
3. Autologous Platelets Have No Effect on the Healing of Human Achilles Tendon Ruptures A Randomized Single-Blind Study
Open this publication in new window or tab >>Autologous Platelets Have No Effect on the Healing of Human Achilles Tendon Ruptures A Randomized Single-Blind Study
Show others...
2011 (English)In: AMERICAN JOURNAL OF SPORTS MEDICINE, ISSN 0363-5465, Vol. 39, no 1, 38-47 p.Article in journal (Refereed) Published
Abstract [en]

Background: Animal studies have shown that local application of platelet-rich plasma (PRP) stimulates tendon repair. Preliminary results from a retrospective case series have shown faster return to sports. Hypothesis: Autologous PRP stimulates healing of acute Achilles tendon ruptures. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: Thirty patients were recruited consecutively. During surgery, tantalum beads were implanted in the Achilles tendon proximal and distal to the rupture. Before skin suture, randomization was performed, and 16 patients were injected with 10 mL PRP (10 times higher platelet concentration than peripheral blood) whereas 14 were not. With 3-dimensional radiographs (roentgen stereophotogrammetric analysis; RSA), the distance between the beads was measured at 7, 19, and 52 weeks while the patient resisted different dorsal flexion moments over the ankle joint, thereby estimating tendon strain per load. An estimate of elasticity modulus was calculated using callus dimensions from computed tomography. At 1 year, functional outcome was evaluated, including the heel raise index and Achilles Tendon Total Rupture Score. The primary effect variables were elasticity modulus at 7 weeks and heel raise index at 1 year. Results: The mechanical variables showed a large degree of variation between patients that could not be explained by measuring error. No significant group differences in elasticity modulus could be shown. There was no significant difference in heel raise index. The Achilles Tendon Total Rupture Score was lower in the PRP group, suggesting a detrimental effect. There was a correlation between the elasticity modulus at 7 and 19 weeks and the heel raise index at 52 weeks. Conclusion: The results suggest that PRP is not useful for treatment of Achilles tendon ruptures. The variation in elasticity modulus provides biologically relevant information, although it is unclear how early biomechanics is connected to late clinical results.

Place, publisher, year, edition, pages
American Journal of Sports Medicine, 2011
Keyword
Achilles tendon, platelet, platelet-rich plasma, tendon healing, biomechanics, roentgen stereophotogrammetric analysis
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-64770 (URN)10.1177/0363546510383515 (DOI)000285874200011 ()
Note
Original Publication: Thorsten Schepull, Joanna Kvist, Hanna Norrman, Marie Trinks, Gösta Berlin and Per Aspenberg, Autologous Platelets Have No Effect on the Healing of Human Achilles Tendon Ruptures A Randomized Single-Blind Study, 2011, AMERICAN JOURNAL OF SPORTS MEDICINE, (39), 1, 38-47. http://dx.doi.org/10.1177/0363546510383515 Copyright: American Journal of Sports Medicine http://www.uk.sagepub.com/Available from: 2011-02-04 Created: 2011-02-04 Last updated: 2015-03-24
4. Early, controlled tension improves the material properties of healing human Achilles tendons after rupture: a randomized trial
Open this publication in new window or tab >>Early, controlled tension improves the material properties of healing human Achilles tendons after rupture: a randomized trial
2013 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Background: Weight-bearing in a fixed brace after acute Achilles tendon rupture does not necessarily lead to mechanical tension in the tendon. Early motion has a positive effect on the clinical outcome, but it is not clear if this is due to effects on tendon strength or to unspecific effects. The aim of this study was to examine if tensional loading leads to improvement of the mechanical properties of the healing, human Achilles tendon.

Hypothesis: The elastic modulus of the tendon callus is increased by early tensional loading.

Study Design: Randomized controlled trial; level of evidence: 2.

Methods: Thirty-five patients with an acute Achilles tendon rupture were recruited consecutively. They were operated with a single suture, and received metal markers in the distal and proximal part of the tendon. After surgery, patients were randomized to either cast immobilization for 7 weeks or tensional loading. The latter group wore a cast for 2 weeks, and then a removable foam walker boot for 5 weeks. They were instructed to remove the boot twice daily and push a special training pedal to produce a predetermined, gradually increasing tensional load on the healing tendon. At 7, 19 and 52 weeks postoperatively, patients were investigated with Roentgen Stereophotogrammetric Analysis (RSA) under different loading conditions, and computed tomography (CT). The collected data allowed calculation of modulus of elasticity. At 52 weeks, we also examined clinical outcome, using the Achilles tendon Total Rupture Score (ATRS) and a heel-raise index.

Results: The elastic modulus at 19 and 52 weeks was higher in the tensional loading group. There was no significant difference in ATRS or heel-raise index at 52 weeks. As in previous studies, there was a significant correlation between the modulus at 7 weeks and the heel-raise index at 52 weeks. There was moderate tendon elongation.

Conclusion: Early tensional loading improves the mechanical properties of the healing Achilles tendon.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-91728 (URN)
Available from: 2013-04-30 Created: 2013-04-30 Last updated: 2013-04-30Bibliographically approved
5. Healing of human Achilles tendon ruptures: Radiodensity reflects mechanical properties
Open this publication in new window or tab >>Healing of human Achilles tendon ruptures: Radiodensity reflects mechanical properties
2015 (English)In: Knee Surgery, Sports Traumatology, Arthroscopy, ISSN 0942-2056, E-ISSN 1433-7347, Vol. 23, no 3, 884-889 p.Article in journal (Refereed) Published
Abstract [en]

Purpose

This study tests the idea of using radiodensity from computed tomography to quantitatively evaluate the healing of ruptured Achilles tendons.

Methods

The radiodensity of the healing tendons in sixty-five patients who were treated for Achilles tendon rupture was measured. The hypothesis was that density would correlate with an estimate for e-modulus, derived from strain, measured by radiostereometry with different mechanical loadings.

Results

Radiodensity 7 weeks after injury was decreased to 67 % (SD 11) of the contralateral, uninjured tendon. There was no improvement in radiodensity from 7 to 19 weeks, whereas at 1 year, it had increased to 106 % (SD 7). Only 2 of 52 measured values at 1 year were lower than the highest value at 19 weeks, i.e. there was minimal overlap. The variation in radiodensity could explain 80 % of the variation in e-modulus, but radiodensity correlated only weakly with e-modulus at each time point separately. At 1 year, both radiodensity and e-modulus correlated with functional results, although weakly.

Conclusions

From 19 weeks onwards, radiodensity appears to reflect mechanical properties of the tendon and might to some extent predict the final outcome. Radiodensity at 7 weeks is difficult to interpret, probably because it reflects both callus and damaged tissues.

Level of evidence

Prospective, diagnostic study, Level II.

National Category
Orthopedics
Identifiers
urn:nbn:se:liu:diva-91725 (URN)10.1007/s00167-013-2720-8 (DOI)000350209300030 ()24162760 (PubMedID)
Available from: 2013-04-30 Created: 2013-04-30 Last updated: 2017-12-06Bibliographically approved

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